Endodontics is a specialized branch of dentistry which deals with the study and care of the tooth pulp. Generally, the study of endodontics centers around the tooth pulp contained within the human tooth. However, endodontics may also involve the study of the teeth of other mammals or even non-mammals. Endodontics and the study and care of the tooth and tooth pulp has been an important and active field for many years.
A substantial portion of the work performed in endodontics involves the study and evaluation of the pulpal vitality and vascular integrity of the tooth. More specifically, endodontics involves evaluating the pulpal vitality and vascular integrity of a tooth in order to diagnose whether or not corrective action, such as a root canal procedure, will be necessary.
An incorrect determination that the tooth pulp is vital or healthy, commonly referred to as a false positive, could result in the delay of necessary treatment. The health of the tooth will continue to erode, often culminating in a painful root canal procedure or in the removal of the tooth. Alternatively, in the event that a healthy tooth pulp is diagnosed incorrectly as being non-vital, commonly referred to as a false negative, it could result in the unnecessary treatment of a healthy tooth and/or its removal. As a result, it is very important for those practicing endodontics to be able accurately to assess the vascular integrity and pulpal vitality of a subject tooth.
As will be described in more detail below, past and current methods practiced to determine tooth vitality have associated therewith several major drawbacks. In order to better describe such drawbacks and the use of the present invention in overcoming these drawbacks, shown in FIG. 1 is a cross-sectional view of a typical human tooth 11. More specifically, the tooth shown in FIG. 1 is a human canine tooth. However, in view of the invention as it is described below, one of ordinary skill will appreciate that such tooth could be another type of tooth, for example, a molar or incisor. Moreover, the tooth 11 need not be that of a human, but may be the tooth of some other animal.
Referring again to FIG. 1, the tooth is made up primarily of a crown section 12 and a root section 14. The crown 12 of the tooth 11 is that section which extends outwardly from the patient's gum 16, above the gum line 17. The root 14 is the portion of the tooth 11 which is located within the patient's gum 16, or below the gum line 17. The outer portion of the crown 12 is made up of a layer of enamel 18. The enamel 18 serves as a hard outer covering to the underlying layer of dentine 20 within the tooth 11.
The dentine 20 is the calcareous part of the tooth 11, below the enamel 18, which contains the pulp chamber 22 and the root canal 23. The pulp chamber 22 is the hollow area in the crown 12 of the tooth which contains the tooth pulp 24 which, as will be appreciated by those of ordinary skill, consists of nerves and blood vessels. The root canal 23 is located in the root 14 of the tooth 10, and serves as a passageway for pulp 24 to enter the pulp chamber 22.
Describing the tooth 11 in more detail, the root canal 23 originates at the base 25 of the root 14. In a healthy tooth 11, the pulp 24 enters the root canal 23 at the base 25 and occupies the entire pulp root canal 23 and the chamber 22 which extends into the crown section 12, as is shown in FIG. 1. It is through the base 25 of the root canal 23 that one or more arteries enter into the tooth 11. The arteries carry the oxygenated blood from the heart into the tooth 11. The arteries travel through the root canal 23 and form many minute capillary beds which terminate in the pulp chamber 22. Subsequently, one or more veins located within the pulp chamber 22 and root canal 23 carry the deoxygenated blood back out of the pulp chamber 22, through the root canal 23, and out through the base 25.
As is mentioned above, in a healthy tooth 11, the pulp 24 occupies the entire pulp chamber 22 and root canal 23, as is shown in FIG. 1. The pulp 24 is nourished by the blood flowing in and out of the root canal 23 into the pulp chamber 22. In turn, the pulp 24 nourishes the tooth itself. However, in an unhealthy tooth, various interruptions in the vascular integrity of the tooth 11 may occur. For example, in the event of pronounced trauma to the tooth, the flow of pulp tissue 24 from the base 25 may be interrupted. The tooth 11 will no longer be nourished by the pulp 24 contained therein. Ultimately, the pulp 24 within the tooth will die, and in the event no corrective care is provided, the tooth may eventually rot.
As another example of an unhealthy tooth, a condition referred to as calcification of the pulp chamber 22 may occur within the pulp chamber 22, thereby causing an interruption in the vascular integrity of the tooth 11. Specifically, calcification of the pulp chamber 22 relates to a condition within the tooth 11 whereby dentine deposits form at the coronal portion 26 of the pulp chamber 22, causing a reduction in the internal volume of the chamber (as is shown in phantom just below the coronal portion 26 in FIG. 1). This results in a degradation of both the amount of pulp present within the tooth 11, and of the vascular integrity of the tooth. Thus, while the pulp 24 within the tooth may remain vital or alive, in an instance such as calcification of the pulp chamber 22, there exists an interruption in the vascular integrity of the tooth 11.
Therefore, it is apparent that the pulpal vitality and the vascular integrity of the tooth 11 must be maintained in order to facilitate the longevity of the tooth. However, while the pulpal vitality and the vascular integrity of the tooth 11 are individual considerations, both are closely related. Therefore, for purposes of this invention, reference to one is intended to be equivalent to reference to the other unless otherwise noted.
For the reasons mentioned above and which are also described in more detail below, in order to provide proper preventive and remedial care to a patient's teeth, the practice of endodontics often requires the ability to evaluate properly the pulpal vitality and vascular integrity of the subject tooth. Those who practice endodontics generally have, in the past, relied on one or two non-invasive methods for evaluating the pulpal vitality and/or vascular integrity of the tooth 11. However, there are significant drawbacks to each of such past methods, as is described below.
In the past, there have been two predominant methods practiced by endodontists for evaluating or determining the pulpal vitality or vascular integrity of a tooth. One method consists of providing electrical stimulation to the subject tooth 11 and determining pulpal vitality based on the conduction of current through the enamel 18 of the tooth 11 into the nerve endings located in the pulp 24 in the pulp chamber 22 and root canal 23 within the tooth. A second method consists of a thermal test in which an extremely hot or cold substance is applied to the enamel 18 of the tooth 11, and pulpal vitality is determined based on whether thermal conduction occurs and is sensed or felt by the patient by way of the nerve endings within the tooth 11. Both methods require a reaction by the patient to pain which is not only uncomfortable but is also extremely subjective since pain tolerance may vary widely from patient to patient.
The electrical stimulation test basically involves attaching an electrode to a portion of the enamel 18 exposed on the crown 12 of the tooth. Typically, a gel toothpaste is used between the electrode and the tooth as a conductive medium. In one manner or another, the patient's body is grounded relative to the electrode. An electrical potential is then applied to the electrode relative to the ground, thereby causing a current to conduct through the tooth 11. More specifically, the current enters through the enamel 18, and is conducted through the dentine 20, through the pulp chamber 22 and out through the root canal 23. Theoretically, if the pulp 24 in the pulp chamber 22 and/or root canal 23 is vital and the nerves contained therein are healthy, the electrical current will stimulate the nerve endings in the pulp 24, resulting in a sharp pain being felt by the patient. Alternatively, if the pulp 24 is non-vital, there will be no nerve stimulation within the tooth 11, and the patient will feel no pain. An exemplary apparatus for performing the electrical stimulation test is the commercially available Model No. 2006 Vitality Scanner manufactured by Analytic Technology.
It is important to note that even if the electrical stimulation test were one hundred percent reliable, the only way to determine tooth vitality using such a method may cause sharp pain for the patient. In the event that the tooth is vital, the patient experiences extreme discomfort. Additionally, longer term ramifications must be considered for the reason that each time the electrical stimulation test is performed, the tooth is subjected to undesirable trauma.
Not only does the electrical stimulation test envelope obvious drawbacks due to patient discomfort and trauma, the electrical stimulation method also significantly produces false positives and/or negatives. For example, a false positive will occur quite often when there is a build up of liquid in the pulp chamber 22 and/or root canal 23 in place of the pulp 24. Such liquid often will build up as a result of infection, or more specifically, as a result of liquefaction necrosis. During the breakdown process, the dying pulp 24 within the tooth may introduce infection. Liquid forms within the pulp chamber 22 as a byproduct of tissue degeneration, as is known by those in the art.
Because the liquid which builds up in the pulp chamber 22 and/or root canal 23 is capable of conducting electrical current, electrical current will still be conducted through the pulp chamber 22 by way of the liquid formed therein, until the current encounters vital pulp 24 further down, in the root canal 23 for example. As a result, pain will still be introduced to the patient by the electrical stimulation of the nerve endings in the root canal 23. Therefore, in the case of liquefaction necrosis, even in the event that pain occurs using the electrical stimulation test, the pulpal vitality or vascular integrity of the tooth is not, in fact, necessarily healthy. In a substantial portion of the pulp chamber 22, in the crown 12 area for example, there may exist only the liquid which has built up. Yet, as the patient may still experience sharp pain, a false positive determination may result.
In addition, a false negative often occurs using the electrical stimulation test. For example, the tooth 11 may be traumatized to the extent that the nerve response within the tooth 11 is interrupted. Somewhat more specifically, oftentimes trauma to the tooth will induce swelling within the tooth. This swelling can interrupt the nerve response either permanently or temporarily, for up to six months or more. Therefore, in actuality, the tooth 11 and pulp 24 contained therein could be alive even though the patient experiences no pain upon the application of an electrical current. Moreover, it need not be trauma to the tooth 11 which produces an interrupted nerve response. Even though pulpal vitality and vascular integrity of the tooth remain intact, various cancers or tumors within the oral structures, for example the jaw bone, can interrupt the response of the nerves entering the tooth 11, as will be appreciated by those of ordinary skill in the art.
The thermal method mentioned above for testing pulpal vitality also has significant drawbacks in much the same manner as does the electrical stimulation test. The thermal method typically consists of either hot or cold testing. During a cold test, a coolant such as the commercially available Frigident is applied to the crown of the tooth using a cotton swab. The temperature of the coolant is such that the cold is thermally conducted through the tooth 11 until it is sensed by the nerves within the pulp chamber 22 and/or root canal 23. When using the heat test to determine pulpal vitality, an extremely hot material is applied to the tooth such that the heat is thermally conducted through the tooth 11 and felt by the nerves therein in the same manner as in the cold test.
Much like the electrical stimulation test, the thermal test is reliant upon a patient with a healthy tooth incurring significant pain in order to positively determine that the vascular integrity of the tooth is intact. Thereby, using the thermal method, a patient with a healthy tooth is likely to be subjected to sharp pain. At least in theory, only a patient with a non-vital tooth will experience no pain as the nerves in the subject tooth will be dead as a result of the deadened pulp 24.
However, for the same reasons which were detailed above, i.e. trauma, the presence of tumors, etc., the nerve response of the tooth 11 may remain deadened while the pulpal vitality and vascular integrity of the tooth remains intact. Thus, even though the tooth is healthy with respect to pulpal vitality, the nerve endings will not sense the thermal change and the thermal test will produce a false negative.
Moreover, the thermal test may also produce a false positive, especially in the situation where the patient previously has undergone significant restoration of the tooth. For example, the subject tooth may have a large filling. Oftentimes, the thermal test will result in a patient feeling pain even though the subject tooth is non-vital. In cases involving significant restoration, the heat or cold will conduct from the subject tooth to one or more neighboring teeth. Thus, the patient still will feel pain. Thus, it is extremely difficult for the patient to determine if the pain is felt by way of the nerves within the subject tooth 11, or by way of the nerves within the neighboring teeth.
In view of the foregoing, it is apparent that the methods practiced in the past for determining tooth vitality were both painful and inaccurate. As mentioned above, and as is described in greater detail below, the present invention relates to the use of oximeter technology for determining tooth vitality, and more specifically, the pulpal vitality and vascular integrity of the tooth. In the past, pulse oximeters have been known in the medical field as a non-invasive monitoring device for determining a patient's oxygen saturation and pulse rate when under intensive care or during sedation procedures. The basic operation of pulse oximeters involves light that is passed from a light emitting diode or other light source through a part of the patient's body, usually the tip of a finger, and into a photodetector or receptor. The difference in intensity of the light emitted and the light received is evaluated, typically using a microprocessor, to provide a pulse rate and oxygen saturation level measurement.
Cited as being of general interest regarding prior art pulse oximeters and the operation and use thereof, are U.S. Pat. Nos. 3,998,550, 4,266,554, 4,586,513, and 4,167,331, the entire disclosures of which are incorporated herein by reference.
Generally, a pulse oximeter measures oxygen saturation in a patient's arterial blood by evaluating the difference between the light absorption coefficient of the hemoglobin and the light absorption coefficient of the hemoglobin oxide in the patient's blood. The amount of light absorbed by the hemoglobin and the hemoglobin oxide in the blood is dependent upon the wavelength of the transmitted light. Typically, the light source emits light of two different wavelengths in order to determine the oxygen saturation of the blood in that portion of the body through which the light is transmitted. The hemoglobin oxide, or the arterial blood, and the de-oxygenated hemoglobin, or the venous blood, each have an effect of the amount of absorbance which occurs with respect to the two wavelengths. It is the ratio of the absorbance of the two wavelengths that determines the percentage of oxygenation of the blood as is known in the art of oximeters. This ratio may take on many forms, as will be appreciated in view of the above mentioned patents. However, the general operation remains the same.
In view of the prior art, it is apparent that the use of the pulse oximeter for measuring the blood oxygen saturation and the pulse rate of a patient is well known. However, until the present invention, there was no accurate, non-invasive device or process for determining the vitality of a human tooth utilizing a pulse oximeter. Instead, for years endodontists have had to rely on such past methods as the above described electrical stimulation test, and the hot and cold thermal tests. As a result, patients have been forced to suffer pain which must be inflicted in order to determine, although inaccurately at times, the pulpal vitality and vascular integrity of the subject tooth.
In view of the foregoing shortcomings of previous methods and techniques for determining tooth vitality, there has existed a strong, long felt need for a tooth vitality probe and process for determining tooth vitality in a painless, non-invasive, accurate manner.